1. Field of the Invention
The present invention relates to a mobile communication system. More specifically, the present invention relates to a mobile communication system which limits use of a calling channel when congestion occurs.
2. Description of the Related Prior Art
Current mobile communication systems have mobile terminals, base stations communicating with the mobile terminals, a home memory managing position information of the mobile terminals, and an exchange station transmitting a call to a public telephone network. In general, due to a disaster or an accident, the number of calls may be temporarily increased abruptly from a certain area. In such case, congestion occurs in the mobile communication system to cause confusion in the network. Japanese Patent Application Laid-Open No. Hei 10-308978 discloses an example of a mobile communication system regulating a call in the above case. Referring to FIG. 1, the mobile communication system has a traffic controller 102 with a home memory 101, a mobile communication exchanger 103, base stations 104, and a plurality of mobile terminals 105. The base station 104 has a regulation part 117 regulating a call from the mobile terminal 105. A traffic measurement part 115 of the mobile communication exchanger 103 measures the number of accesses to transmit it to the traffic controller 102. The home memory 101 stores information of the mobile terminal. A congestion detection part 111 accesses the home memory 101 to detect congestion. A regulation decision part 113 decides the base station regulated based on the detected result. A regulation indication part 114 calculates a regulation amount to send it to the targeted mobile communication exchanger 103. A regulation amount distribution part 116 distributes the regulation amount to the base station 104 at a predetermined rate. The regulation part 117 of the base station 104 regulates the call from the mobile terminal 105 at the notified rate.
In the mobile communication system, however, the regulation part 117 automatically disconnects the call at the predetermined rate. An emergency call may be disconnected.